1 /* 2 * Device operations for the pnfs nfs4 file layout driver. 3 * 4 * Copyright (c) 2014, Primary Data, Inc. All rights reserved. 5 * 6 * Tao Peng <bergwolf@primarydata.com> 7 */ 8 9 #include <linux/nfs_fs.h> 10 #include <linux/vmalloc.h> 11 #include <linux/module.h> 12 #include <linux/sunrpc/addr.h> 13 14 #include "../internal.h" 15 #include "../nfs4session.h" 16 #include "flexfilelayout.h" 17 18 #define NFSDBG_FACILITY NFSDBG_PNFS_LD 19 20 static unsigned int dataserver_timeo = NFS_DEF_TCP_RETRANS; 21 static unsigned int dataserver_retrans; 22 23 static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg); 24 25 void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds) 26 { 27 if (!IS_ERR_OR_NULL(mirror_ds)) 28 nfs4_put_deviceid_node(&mirror_ds->id_node); 29 } 30 31 void nfs4_ff_layout_free_deviceid(struct nfs4_ff_layout_ds *mirror_ds) 32 { 33 nfs4_print_deviceid(&mirror_ds->id_node.deviceid); 34 nfs4_pnfs_ds_put(mirror_ds->ds); 35 kfree_rcu(mirror_ds, id_node.rcu); 36 } 37 38 /* Decode opaque device data and construct new_ds using it */ 39 struct nfs4_ff_layout_ds * 40 nfs4_ff_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev, 41 gfp_t gfp_flags) 42 { 43 struct xdr_stream stream; 44 struct xdr_buf buf; 45 struct page *scratch; 46 struct list_head dsaddrs; 47 struct nfs4_pnfs_ds_addr *da; 48 struct nfs4_ff_layout_ds *new_ds = NULL; 49 struct nfs4_ff_ds_version *ds_versions = NULL; 50 u32 mp_count; 51 u32 version_count; 52 __be32 *p; 53 int i, ret = -ENOMEM; 54 55 /* set up xdr stream */ 56 scratch = alloc_page(gfp_flags); 57 if (!scratch) 58 goto out_err; 59 60 new_ds = kzalloc(sizeof(struct nfs4_ff_layout_ds), gfp_flags); 61 if (!new_ds) 62 goto out_scratch; 63 64 nfs4_init_deviceid_node(&new_ds->id_node, 65 server, 66 &pdev->dev_id); 67 INIT_LIST_HEAD(&dsaddrs); 68 69 xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen); 70 xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE); 71 72 /* multipath count */ 73 p = xdr_inline_decode(&stream, 4); 74 if (unlikely(!p)) 75 goto out_err_drain_dsaddrs; 76 mp_count = be32_to_cpup(p); 77 dprintk("%s: multipath ds count %d\n", __func__, mp_count); 78 79 for (i = 0; i < mp_count; i++) { 80 /* multipath ds */ 81 da = nfs4_decode_mp_ds_addr(server->nfs_client->cl_net, 82 &stream, gfp_flags); 83 if (da) 84 list_add_tail(&da->da_node, &dsaddrs); 85 } 86 if (list_empty(&dsaddrs)) { 87 dprintk("%s: no suitable DS addresses found\n", 88 __func__); 89 ret = -ENOMEDIUM; 90 goto out_err_drain_dsaddrs; 91 } 92 93 /* version count */ 94 p = xdr_inline_decode(&stream, 4); 95 if (unlikely(!p)) 96 goto out_err_drain_dsaddrs; 97 version_count = be32_to_cpup(p); 98 dprintk("%s: version count %d\n", __func__, version_count); 99 100 ds_versions = kzalloc(version_count * sizeof(struct nfs4_ff_ds_version), 101 gfp_flags); 102 if (!ds_versions) 103 goto out_scratch; 104 105 for (i = 0; i < version_count; i++) { 106 /* 20 = version(4) + minor_version(4) + rsize(4) + wsize(4) + 107 * tightly_coupled(4) */ 108 p = xdr_inline_decode(&stream, 20); 109 if (unlikely(!p)) 110 goto out_err_drain_dsaddrs; 111 ds_versions[i].version = be32_to_cpup(p++); 112 ds_versions[i].minor_version = be32_to_cpup(p++); 113 ds_versions[i].rsize = nfs_block_size(be32_to_cpup(p++), NULL); 114 ds_versions[i].wsize = nfs_block_size(be32_to_cpup(p++), NULL); 115 ds_versions[i].tightly_coupled = be32_to_cpup(p); 116 117 if (ds_versions[i].rsize > NFS_MAX_FILE_IO_SIZE) 118 ds_versions[i].rsize = NFS_MAX_FILE_IO_SIZE; 119 if (ds_versions[i].wsize > NFS_MAX_FILE_IO_SIZE) 120 ds_versions[i].wsize = NFS_MAX_FILE_IO_SIZE; 121 122 /* 123 * check for valid major/minor combination. 124 * currently we support dataserver which talk: 125 * v3, v4.0, v4.1, v4.2 126 */ 127 if (!((ds_versions[i].version == 3 && ds_versions[i].minor_version == 0) || 128 (ds_versions[i].version == 4 && ds_versions[i].minor_version < 3))) { 129 dprintk("%s: [%d] unsupported ds version %d-%d\n", __func__, 130 i, ds_versions[i].version, 131 ds_versions[i].minor_version); 132 ret = -EPROTONOSUPPORT; 133 goto out_err_drain_dsaddrs; 134 } 135 136 dprintk("%s: [%d] vers %u minor_ver %u rsize %u wsize %u coupled %d\n", 137 __func__, i, ds_versions[i].version, 138 ds_versions[i].minor_version, 139 ds_versions[i].rsize, 140 ds_versions[i].wsize, 141 ds_versions[i].tightly_coupled); 142 } 143 144 new_ds->ds_versions = ds_versions; 145 new_ds->ds_versions_cnt = version_count; 146 147 new_ds->ds = nfs4_pnfs_ds_add(&dsaddrs, gfp_flags); 148 if (!new_ds->ds) 149 goto out_err_drain_dsaddrs; 150 151 /* If DS was already in cache, free ds addrs */ 152 while (!list_empty(&dsaddrs)) { 153 da = list_first_entry(&dsaddrs, 154 struct nfs4_pnfs_ds_addr, 155 da_node); 156 list_del_init(&da->da_node); 157 kfree(da->da_remotestr); 158 kfree(da); 159 } 160 161 __free_page(scratch); 162 return new_ds; 163 164 out_err_drain_dsaddrs: 165 while (!list_empty(&dsaddrs)) { 166 da = list_first_entry(&dsaddrs, struct nfs4_pnfs_ds_addr, 167 da_node); 168 list_del_init(&da->da_node); 169 kfree(da->da_remotestr); 170 kfree(da); 171 } 172 173 kfree(ds_versions); 174 out_scratch: 175 __free_page(scratch); 176 out_err: 177 kfree(new_ds); 178 179 dprintk("%s ERROR: returning %d\n", __func__, ret); 180 return NULL; 181 } 182 183 static void ff_layout_mark_devid_invalid(struct pnfs_layout_segment *lseg, 184 struct nfs4_deviceid_node *devid) 185 { 186 nfs4_delete_deviceid(devid->ld, devid->nfs_client, &devid->deviceid); 187 if (!ff_layout_has_available_ds(lseg)) 188 pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode, 189 lseg); 190 } 191 192 static bool ff_layout_mirror_valid(struct pnfs_layout_segment *lseg, 193 struct nfs4_ff_layout_mirror *mirror, 194 bool create) 195 { 196 if (mirror == NULL || IS_ERR(mirror->mirror_ds)) 197 goto outerr; 198 if (mirror->mirror_ds == NULL) { 199 if (create) { 200 struct nfs4_deviceid_node *node; 201 struct pnfs_layout_hdr *lh = lseg->pls_layout; 202 struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV); 203 204 node = nfs4_find_get_deviceid(NFS_SERVER(lh->plh_inode), 205 &mirror->devid, lh->plh_lc_cred, 206 GFP_KERNEL); 207 if (node) 208 mirror_ds = FF_LAYOUT_MIRROR_DS(node); 209 210 /* check for race with another call to this function */ 211 if (cmpxchg(&mirror->mirror_ds, NULL, mirror_ds) && 212 mirror_ds != ERR_PTR(-ENODEV)) 213 nfs4_put_deviceid_node(node); 214 } else 215 goto outerr; 216 } 217 218 if (IS_ERR(mirror->mirror_ds)) 219 goto outerr; 220 221 if (mirror->mirror_ds->ds == NULL) { 222 struct nfs4_deviceid_node *devid; 223 devid = &mirror->mirror_ds->id_node; 224 ff_layout_mark_devid_invalid(lseg, devid); 225 return false; 226 } 227 return true; 228 outerr: 229 pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode, lseg); 230 return false; 231 } 232 233 static void extend_ds_error(struct nfs4_ff_layout_ds_err *err, 234 u64 offset, u64 length) 235 { 236 u64 end; 237 238 end = max_t(u64, pnfs_end_offset(err->offset, err->length), 239 pnfs_end_offset(offset, length)); 240 err->offset = min_t(u64, err->offset, offset); 241 err->length = end - err->offset; 242 } 243 244 static int 245 ff_ds_error_match(const struct nfs4_ff_layout_ds_err *e1, 246 const struct nfs4_ff_layout_ds_err *e2) 247 { 248 int ret; 249 250 if (e1->opnum != e2->opnum) 251 return e1->opnum < e2->opnum ? -1 : 1; 252 if (e1->status != e2->status) 253 return e1->status < e2->status ? -1 : 1; 254 ret = memcmp(e1->stateid.data, e2->stateid.data, 255 sizeof(e1->stateid.data)); 256 if (ret != 0) 257 return ret; 258 ret = memcmp(&e1->deviceid, &e2->deviceid, sizeof(e1->deviceid)); 259 if (ret != 0) 260 return ret; 261 if (pnfs_end_offset(e1->offset, e1->length) < e2->offset) 262 return -1; 263 if (e1->offset > pnfs_end_offset(e2->offset, e2->length)) 264 return 1; 265 /* If ranges overlap or are contiguous, they are the same */ 266 return 0; 267 } 268 269 static void 270 ff_layout_add_ds_error_locked(struct nfs4_flexfile_layout *flo, 271 struct nfs4_ff_layout_ds_err *dserr) 272 { 273 struct nfs4_ff_layout_ds_err *err, *tmp; 274 struct list_head *head = &flo->error_list; 275 int match; 276 277 /* Do insertion sort w/ merges */ 278 list_for_each_entry_safe(err, tmp, &flo->error_list, list) { 279 match = ff_ds_error_match(err, dserr); 280 if (match < 0) 281 continue; 282 if (match > 0) { 283 /* Add entry "dserr" _before_ entry "err" */ 284 head = &err->list; 285 break; 286 } 287 /* Entries match, so merge "err" into "dserr" */ 288 extend_ds_error(dserr, err->offset, err->length); 289 list_replace(&err->list, &dserr->list); 290 kfree(err); 291 return; 292 } 293 294 list_add_tail(&dserr->list, head); 295 } 296 297 int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo, 298 struct nfs4_ff_layout_mirror *mirror, u64 offset, 299 u64 length, int status, enum nfs_opnum4 opnum, 300 gfp_t gfp_flags) 301 { 302 struct nfs4_ff_layout_ds_err *dserr; 303 304 if (status == 0) 305 return 0; 306 307 if (mirror->mirror_ds == NULL) 308 return -EINVAL; 309 310 dserr = kmalloc(sizeof(*dserr), gfp_flags); 311 if (!dserr) 312 return -ENOMEM; 313 314 INIT_LIST_HEAD(&dserr->list); 315 dserr->offset = offset; 316 dserr->length = length; 317 dserr->status = status; 318 dserr->opnum = opnum; 319 nfs4_stateid_copy(&dserr->stateid, &mirror->stateid); 320 memcpy(&dserr->deviceid, &mirror->mirror_ds->id_node.deviceid, 321 NFS4_DEVICEID4_SIZE); 322 323 spin_lock(&flo->generic_hdr.plh_inode->i_lock); 324 ff_layout_add_ds_error_locked(flo, dserr); 325 spin_unlock(&flo->generic_hdr.plh_inode->i_lock); 326 327 return 0; 328 } 329 330 static struct rpc_cred * 331 ff_layout_get_mirror_cred(struct nfs4_ff_layout_mirror *mirror, u32 iomode) 332 { 333 struct rpc_cred *cred, __rcu **pcred; 334 335 if (iomode == IOMODE_READ) 336 pcred = &mirror->ro_cred; 337 else 338 pcred = &mirror->rw_cred; 339 340 rcu_read_lock(); 341 do { 342 cred = rcu_dereference(*pcred); 343 if (!cred) 344 break; 345 346 cred = get_rpccred_rcu(cred); 347 } while(!cred); 348 rcu_read_unlock(); 349 return cred; 350 } 351 352 struct nfs_fh * 353 nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx) 354 { 355 struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, mirror_idx); 356 struct nfs_fh *fh = NULL; 357 358 if (!ff_layout_mirror_valid(lseg, mirror, false)) { 359 pr_err_ratelimited("NFS: %s: No data server for mirror offset index %d\n", 360 __func__, mirror_idx); 361 goto out; 362 } 363 364 /* FIXME: For now assume there is only 1 version available for the DS */ 365 fh = &mirror->fh_versions[0]; 366 out: 367 return fh; 368 } 369 370 /** 371 * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call 372 * @lseg: the layout segment we're operating on 373 * @ds_idx: index of the DS to use 374 * @fail_return: return layout on connect failure? 375 * 376 * Try to prepare a DS connection to accept an RPC call. This involves 377 * selecting a mirror to use and connecting the client to it if it's not 378 * already connected. 379 * 380 * Since we only need a single functioning mirror to satisfy a read, we don't 381 * want to return the layout if there is one. For writes though, any down 382 * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish 383 * between the two cases. 384 * 385 * Returns a pointer to a connected DS object on success or NULL on failure. 386 */ 387 struct nfs4_pnfs_ds * 388 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx, 389 bool fail_return) 390 { 391 struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx); 392 struct nfs4_pnfs_ds *ds = NULL; 393 struct nfs4_deviceid_node *devid; 394 struct inode *ino = lseg->pls_layout->plh_inode; 395 struct nfs_server *s = NFS_SERVER(ino); 396 unsigned int max_payload; 397 int status; 398 399 if (!ff_layout_mirror_valid(lseg, mirror, true)) { 400 pr_err_ratelimited("NFS: %s: No data server for offset index %d\n", 401 __func__, ds_idx); 402 goto out; 403 } 404 405 devid = &mirror->mirror_ds->id_node; 406 if (ff_layout_test_devid_unavailable(devid)) 407 goto out_fail; 408 409 ds = mirror->mirror_ds->ds; 410 /* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */ 411 smp_rmb(); 412 if (ds->ds_clp) 413 goto out; 414 415 /* FIXME: For now we assume the server sent only one version of NFS 416 * to use for the DS. 417 */ 418 status = nfs4_pnfs_ds_connect(s, ds, devid, dataserver_timeo, 419 dataserver_retrans, 420 mirror->mirror_ds->ds_versions[0].version, 421 mirror->mirror_ds->ds_versions[0].minor_version); 422 423 /* connect success, check rsize/wsize limit */ 424 if (!status) { 425 max_payload = 426 nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient), 427 NULL); 428 if (mirror->mirror_ds->ds_versions[0].rsize > max_payload) 429 mirror->mirror_ds->ds_versions[0].rsize = max_payload; 430 if (mirror->mirror_ds->ds_versions[0].wsize > max_payload) 431 mirror->mirror_ds->ds_versions[0].wsize = max_payload; 432 goto out; 433 } 434 out_fail: 435 ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout), 436 mirror, lseg->pls_range.offset, 437 lseg->pls_range.length, NFS4ERR_NXIO, 438 OP_ILLEGAL, GFP_NOIO); 439 if (fail_return || !ff_layout_has_available_ds(lseg)) 440 pnfs_error_mark_layout_for_return(ino, lseg); 441 ds = NULL; 442 out: 443 return ds; 444 } 445 446 struct rpc_cred * 447 ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg, u32 ds_idx, 448 struct rpc_cred *mdscred) 449 { 450 struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx); 451 struct rpc_cred *cred; 452 453 if (mirror) { 454 cred = ff_layout_get_mirror_cred(mirror, lseg->pls_range.iomode); 455 if (!cred) 456 cred = get_rpccred(mdscred); 457 } else { 458 cred = get_rpccred(mdscred); 459 } 460 return cred; 461 } 462 463 /** 464 * Find or create a DS rpc client with th MDS server rpc client auth flavor 465 * in the nfs_client cl_ds_clients list. 466 */ 467 struct rpc_clnt * 468 nfs4_ff_find_or_create_ds_client(struct pnfs_layout_segment *lseg, u32 ds_idx, 469 struct nfs_client *ds_clp, struct inode *inode) 470 { 471 struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx); 472 473 switch (mirror->mirror_ds->ds_versions[0].version) { 474 case 3: 475 /* For NFSv3 DS, flavor is set when creating DS connections */ 476 return ds_clp->cl_rpcclient; 477 case 4: 478 return nfs4_find_or_create_ds_client(ds_clp, inode); 479 default: 480 BUG(); 481 } 482 } 483 484 void ff_layout_free_ds_ioerr(struct list_head *head) 485 { 486 struct nfs4_ff_layout_ds_err *err; 487 488 while (!list_empty(head)) { 489 err = list_first_entry(head, 490 struct nfs4_ff_layout_ds_err, 491 list); 492 list_del(&err->list); 493 kfree(err); 494 } 495 } 496 497 /* called with inode i_lock held */ 498 int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head) 499 { 500 struct nfs4_ff_layout_ds_err *err; 501 __be32 *p; 502 503 list_for_each_entry(err, head, list) { 504 /* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE) 505 * + array length + deviceid(NFS4_DEVICEID4_SIZE) 506 * + status(4) + opnum(4) 507 */ 508 p = xdr_reserve_space(xdr, 509 28 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE); 510 if (unlikely(!p)) 511 return -ENOBUFS; 512 p = xdr_encode_hyper(p, err->offset); 513 p = xdr_encode_hyper(p, err->length); 514 p = xdr_encode_opaque_fixed(p, &err->stateid, 515 NFS4_STATEID_SIZE); 516 /* Encode 1 error */ 517 *p++ = cpu_to_be32(1); 518 p = xdr_encode_opaque_fixed(p, &err->deviceid, 519 NFS4_DEVICEID4_SIZE); 520 *p++ = cpu_to_be32(err->status); 521 *p++ = cpu_to_be32(err->opnum); 522 dprintk("%s: offset %llu length %llu status %d op %d\n", 523 __func__, err->offset, err->length, err->status, 524 err->opnum); 525 } 526 527 return 0; 528 } 529 530 static 531 unsigned int do_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo, 532 const struct pnfs_layout_range *range, 533 struct list_head *head, 534 unsigned int maxnum) 535 { 536 struct nfs4_flexfile_layout *flo = FF_LAYOUT_FROM_HDR(lo); 537 struct inode *inode = lo->plh_inode; 538 struct nfs4_ff_layout_ds_err *err, *n; 539 unsigned int ret = 0; 540 541 spin_lock(&inode->i_lock); 542 list_for_each_entry_safe(err, n, &flo->error_list, list) { 543 if (!pnfs_is_range_intersecting(err->offset, 544 pnfs_end_offset(err->offset, err->length), 545 range->offset, 546 pnfs_end_offset(range->offset, range->length))) 547 continue; 548 if (!maxnum) 549 break; 550 list_move(&err->list, head); 551 maxnum--; 552 ret++; 553 } 554 spin_unlock(&inode->i_lock); 555 return ret; 556 } 557 558 unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo, 559 const struct pnfs_layout_range *range, 560 struct list_head *head, 561 unsigned int maxnum) 562 { 563 unsigned int ret; 564 565 ret = do_layout_fetch_ds_ioerr(lo, range, head, maxnum); 566 /* If we're over the max, discard all remaining entries */ 567 if (ret == maxnum) { 568 LIST_HEAD(discard); 569 do_layout_fetch_ds_ioerr(lo, range, &discard, -1); 570 ff_layout_free_ds_ioerr(&discard); 571 } 572 return ret; 573 } 574 575 static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg) 576 { 577 struct nfs4_ff_layout_mirror *mirror; 578 struct nfs4_deviceid_node *devid; 579 u32 idx; 580 581 for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) { 582 mirror = FF_LAYOUT_COMP(lseg, idx); 583 if (mirror) { 584 if (!mirror->mirror_ds) 585 return true; 586 if (IS_ERR(mirror->mirror_ds)) 587 continue; 588 devid = &mirror->mirror_ds->id_node; 589 if (!ff_layout_test_devid_unavailable(devid)) 590 return true; 591 } 592 } 593 594 return false; 595 } 596 597 static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg) 598 { 599 struct nfs4_ff_layout_mirror *mirror; 600 struct nfs4_deviceid_node *devid; 601 u32 idx; 602 603 for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) { 604 mirror = FF_LAYOUT_COMP(lseg, idx); 605 if (!mirror || IS_ERR(mirror->mirror_ds)) 606 return false; 607 if (!mirror->mirror_ds) 608 continue; 609 devid = &mirror->mirror_ds->id_node; 610 if (ff_layout_test_devid_unavailable(devid)) 611 return false; 612 } 613 614 return FF_LAYOUT_MIRROR_COUNT(lseg) != 0; 615 } 616 617 static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg) 618 { 619 if (lseg->pls_range.iomode == IOMODE_READ) 620 return ff_read_layout_has_available_ds(lseg); 621 /* Note: RW layout needs all mirrors available */ 622 return ff_rw_layout_has_available_ds(lseg); 623 } 624 625 bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg) 626 { 627 return ff_layout_no_fallback_to_mds(lseg) || 628 ff_layout_has_available_ds(lseg); 629 } 630 631 bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg) 632 { 633 return lseg->pls_range.iomode == IOMODE_RW && 634 ff_layout_no_read_on_rw(lseg); 635 } 636 637 module_param(dataserver_retrans, uint, 0644); 638 MODULE_PARM_DESC(dataserver_retrans, "The number of times the NFSv4.1 client " 639 "retries a request before it attempts further " 640 " recovery action."); 641 module_param(dataserver_timeo, uint, 0644); 642 MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the " 643 "NFSv4.1 client waits for a response from a " 644 " data server before it retries an NFS request."); 645